1. Field of the Invention
The present invention relates generally to lifters and, more particularly, is concerned with a lifter for a manhole cover.
2. Description of the Prior Art
Manhole cover lifters have been described in the prior art; however, none of the prior art devices disclose the unique features of the present invention.
In U.S. Pat. No. 2,832,628, dated Apr. 29, 1958, Turnbull disclosed an improved lifter for loosening and lifting manhole covers. The principal object of the invention is to provide a simple, strong and sturdy manhole cover lifter, which will loosen and lift manhole covers of different sizes and weights. The lifter comprises an operating level which can be operated by one man to loosen the cover, lift it up and swing it laterally away from the manhole.
In U.S. Pat. No. 6,439,628 B1, dated Aug. 27, 2002, Estambolchi, et al., disclosed a durable cover lifting tool which includes three separate pieces that are mated together to allow for the entire cover to be lifted in one motion. A pair of hook arms are inserted over opposing holes in the manhole cover and joined together. A lifting arm is then attached to the joined hook arms and used to remove the cover from the opening.
In U.S. Pat. No. 4,482,182, dated Nov. 13, 2984, Mortensen disclosed a tool which is suitable for lifting a manhole lid that has spaced attachment notches in its top surface. In one embodiment, the tool has a substantially rigid support beam. The beam has a first hook adjacent to its forward end which is adapted to be inserted in one of the notches. The beam also has a pivot attachment point adjacent the rear end of the beam. There is provided a second hook which is mounted on the pivot attachment point, the second hook being adapted to be inserted in a second of the notches upon a pivoting of the hook relative to the beam. The hooks will then act to grip the lid between them. To provide a secure grip to grip the lid between them. To provide a secure grip on the lid, there is provided a catch which prevents the second hook from pivoting back out of the second notch until the catch is released. This catch automatically locks the second hook in the second notch upon movement of the second hook into the second notch.
In U.S. Pat. No. 1,933,384, dated Oct. 31, 1933, Moyian disclosed a device for lifting valve covers, manhole covers, sewer covers, and the like and which is to provide a simple, durable and efficient device of this character which may be manufactured at small cost and is well adapted for the purpose intended.
In U.S. Pat. No. 5,775,674, dated Jul. 7, 1998, Bigham disclosed a lift device for lifting a manhole cover which includes a base and a pole configured to lift the manhole cover when one end of the pole is pressed downward. The length of the pole is adjustable in order to permit easy storage and transportation, and to increase the lift force. Retainers are configured to secure manhole covers to the lift device to permit the lifting of the manhole covers in a manner that their center of mass is kept near the end of the pole.
In U.S. Pat. No. 3,985,338, dated Oct. 12, 1976, Herrmann disclosed a tool for breaking loose a manhole cover which has become sealed under an accumulation of road tar and dirt, the device consisting of a long lever which at one end has a hook for engaging an opening through the manhole cover, a fulcrum being located relatively close to the end of the lever having the hook, so that when a workman places his foot upon the other end of the lever, he can with very little effort pry the manhole upwardly for easy removal.
In U.S. Pat. No. 4,157,810, dated Jun. 12, 1979, Haller, et al., disclosed an apparatus for lifting a manhole cover which comprises (1) a means for engaging the manhole cover which cooperates with a lever means for raising the cover, and (2) a pivot means which also cooperates with the level means to pivot the cover to the desired position.
In U.S. Pat. No. 4,365,925, dated Dec. 28, 1982, Girtz disclosed a manhole cover lifter comprising an elongate inclined lever with a handle at its upper end and a fastener at its lower end for attaching to the cover of a manhole; a depending strut intermediate the ends of the lever and a pair of wheels mounted at the lower end of the strut and on a transverse axis forming a fulcrum for the lifting lever; a lifter bar connecting the wheel axle with the forward end of the lifter bar, the lifting lever being of tubular steel and a stiffener bar in the tubular level at the upper end of the depending strut; and a handle at the upper end of the lifting lever.
While these lifters for manhole covers may be suitable for the purposes for which they were designed, they would not be as suitable for the purposes of the present invention, as hereinafter described.